That is a difficult call.  There are many older half-room models around which make set lighting a nightmare where IBL and IDL are concerned.  Some users complete the rooms by adding flat planes to take advantage of the IDL feature.  Others use a darkened dome to simulate the same thing.  And becomes even tougher when a daytime image is used on the dome and your room is incomplete.  If I had to chose between IBL and IDL, IDL would be my preference.  I have found that IBL ambient lighting is too far reaching; it must be used at very low intensities or it will overpower your shadowed areas.  It is very indiscriminant. 

For indoor scenes, multiple lights is perfectly acceptable.  You are trying to simulate an interior stage which may have several light sources for illumination.  The purpose is to duplicate real lighting situations.  Try decreasing the ambient value of your dome so it's intensity won't interfere with your stage lighting.